sync, assistant: Sync with remotes that have annex-ignore set

This is so git remotes on servers without git-annex installed can be used
to keep clients' git repos in sync.

This is a behavior change, but since annex-sync can be set to disable
syncing with a remote, I think it's acceptable.

Assistant/Sync.hs

@@ -68,7 +68,9 @@ reconnectRemotes notifypushes rs = void $ do
 	go = do
 		(failed, diverged) <- sync
 			=<< liftAnnex (inRepo Git.Branch.current)
-		addScanRemotes diverged nonxmppremotes
+		addScanRemotes diverged $
+			filter (not . remoteAnnexIgnore . Remote.gitconfig)
+				nonxmppremotes
 		return failed
 
 {- Updates the local sync branch, then pushes it to all remotes, in